The invention relates generally to tripot-type constant-velocity joints for motor vehicle drivelines.
The present invention relates to a rolling bearing assembly of the type comprising an inner ring, an outer roller surrounding the inner ring, a needle race placed between the inner ring and the outer roller to allow their relative pivoting about a common longitudinal axis, and an axial retaining assembly for retaining the outer roller and the needle race with respect to the inner ring. The retaining assembly comprise at least one split thrust washer which extends radially only from a radially outer region of an axially outer surface of the inner ring towards a retaining groove formed radially inside the outer roller.
In general, assemblies of the aforementioned type used in applications, such as motor vehicle drivelines, each have two split washers, arranged axially one on each side of the inner ring and covering the needle race. The outer peripheral edge of each of these washers is engaged in a respective annular retaining groove formed in the outer roller.
It is necessary for these split washers to be deformed elastically in order to insert them in the grooves in the outer roller.
The thickness of these thrust washers is dictated, according to the material used, by considerations of limiting the risks of these washers going into xe2x80x9cconical deformationxe2x80x9d under the effect of an axial load.
In consequence, the ability of such a washer to deform may be measured by the coefficient C=R/L where L is the radial width of the washer and R is its outside radius.
The higher the coefficient C, the greater the ability to deform the washer and the easier it is to fit.
The width L is slightly greater than the sum of the diameter of the needles, the distance over which the washer bears on the inner ring, and the distance over which the washer bears in the corresponding groove of the outer roller. In general, these two bearing distances have to be greater than 0.8 mm. Likewise, there is a minimum diameter imposed on the needles; their diameter having to be greater than the width of the slit in the split washer once the latter has been engaged in the corresponding groove in the outer roller.
Thus, in practice, it is not possible to vary L below a minimum value of about 3 mm.
In the case of small-sized drivelines, that is to say when R is small, the coefficient C may then be too low for it to be possible to assemble the driveline.
An object of the present invention is to solve this problem by providing a rolling bearing assembly of the aforementioned type which is easier to assemble and which can be made with relatively small dimensions.
To this end, the subject of the invention is a rolling bearing assembly of the aforementioned type, characterized in that the split washer comprises an annular central zone for axially retaining the needle race, and at least one series of peripheral supports which are spaced apart and which radially extend the annular central zone.
According to particular embodiments, the rolling bearing assembly may have one or more of the following features, taken in isolation or in any technically feasible combination.
The split washer may comprise a series of inner peripheral supports which are spaced apart and which extend the annular central zone towards the radially outer region of the axially outer surface of the inner ring. In addition, the split washer may comprise a series of outer peripheral supports which are spaced apart and which extend the annular central zone towards the retaining groove of the outer roller.
The rolling bearing assembly may include inner peripheral supports, which are angularly offset from outer peripheral supports, and/or inner and outer peripheral supports are practically radially aligned. In addition, the supports or each series of peripheral supports can be angularly distributed substantially uniformly.
The slit of the split washer may also be adjacent to at least one peripheral support, particularly an outer peripheral support. Also, a region of the split washer that is diametrically opposite the slit of the split washer may have at most one peripheral support.
The said washer may be formed of a strip of substantially constant width which is spaced from the longitudinal axis by a distance which varies along its periphery, so as to form inner and outer peripheral supports, alternately. The strip may also undulate about a pitch circle.
The split washer may also have a polygonal overall shape, the corners of which form outer peripheral supports, and the middle parts of the sides of which form inner peripheral supports.
The retaining groove is a groove that houses the needle race. The retaining assembly may comprise two split thrust washers arranged axially one on each side of the bearing assembly, these washers extending radially, covering the needle race, from radially outer regions of two axially outer surfaces of the inner ring as far as a common retaining groove formed radially inside the outer roller, and the common groove is the groove that houses the needle race. The groove that houses the needle race has a bottom which on the one hand forms a raceway for the needle race and on the other hand forms a thrust surface for each split washer, and the bottom has a substantially straight profile with a tolerance of within 0.5 mm.
Another subject of the invention is a constant velocity universal joint comprising a male element with a number of arms, a female element delimiting two runway tracks for each arm and, for each arm, a rolling bearing assembly mounted on the arm. This bearing assembly comprises an inner ring pivoting about the arm, an outer roller surrounding the inner ring and running along the two runway tracks, and a needle race placed between the inner ring and the outer roller to allow their relative pivoting about a common longitudinal axis, characterized in that at least one rolling bearing assembly is an assembly as described hereinabove.